Conventionally, automobiles include an antilock brake system for preventing the wheels from locking at the time of braking, a traction control system for preventing the wheels from slipping when the automobile starts to move, and the like, and wheel speed sensors for accurately measuring the rotational speed of the wheels are widely used as parts of such systems.
For example, JP 2007-170963A (Patent Document 1) discloses such a wheel speed sensor that has a configuration in which a rotation detection element that detects a magnetic field fluctuation caused by rotation of a rotor, which rotates together with the wheels and serves as a detection target, and converts the detected fluctuation into an electric signal, and parts of a pair of output wires connected to a pair of lead sections of this rotation detection element are buried in and covered with a synthetic resin cover part. Furthermore, the wheel speed sensor is configured to be fixed to the vehicle side via a fixation part provided on the cover part.
Meanwhile, in the wheel speed sensor having the conventional structure as described in Patent Document 1, the cover part is circumferentially molded directly on the outer circumferential surface of an exterior material provided externally on the output wires, and the cover part and the exterior material are fused to each other to ensure water stopping properties of the drawn-out portions of the output wires, in order to prevent water from entering the inside of the cover part via the output wires.
However, due to an increase in the number of in-vehicle electronic components in recent years, there are more and more cases where another electronic component is installed in the vicinity of the wheel speed sensor. In such a case, by putting the output wires of the wheel speed sensor and the output wires of the other electronic component together and accommodating them in a single exterior material so as to form one wire harness, reductions in the number of processing steps and in the cost are achieved. Accordingly, there are cases where the conventional water-stopping structure in which the output wires for the wheel speed sensor are fused to the cover part of the wheel speed sensor while being accommodated in the exterior material cannot be employed.
In other words, when output wires for a wheel speed sensor and output wires of another electronic component are accommodated in one exterior material so as to configure a wire harness, it is necessary to remove the exterior material of the wire harness in the vicinity of the wheel speed sensor to guide out the output wires for the wheel speed sensor, and to fuse the output wires directly to the cover part. However, the output wires for the wheel speed sensor are often coated with a synthetic resin material that is not likely to be fused to the cover part of the wheel speed sensor, and thus a gap may be created between the cover part and the output wires, making it difficult to ensure the waterproof property.